Stamatia-Maria Rapti, Diana Augustdottir, Zarko Urosevic and Erna Magnusdottir
Waldenström Macroglobulinemia (WM) is an incurable B-cell lymphoma characterized by a range of cell phenotypes from B-cells to plasma cells. The transcription factor BLIMP1 is a crucial regulator for the plasma cell differentiation program.
To investigate BLIMP1’s role in WM, we used the RPCI-WM1 cell line engineered to express a doxycycline-induced microRNA targeting endogenous BLIMP1 for knockdown (KD). We further engineered the KD cell line to overexpress BLIMP1 via a lentivirally delivered Destabilization Domain EGFP-BLIMP1, which is continuously degraded unless protected by the Shield-1 molecule.
Our experiments reveal a correlation between BLIMP1 levels and double-strand breaks (DSB), particularly outside S-Phase. BLIMP1 overexpression results in 25% fewer DSBs than KD, with KD leading to cell death by day six. To understand BLIMP1’s impact on the cell cycle and cell death, we used EdU, a thymidine analog incorporated during DNA replication. After 48 hours of BLIMP1 KD induction, 62%±3.6 of cells are in G1, and 20%±1.5 are apoptotic, compared to 54%±2.5 and 5.9%±0.1 in control cells. Overexpressing BLIMP1 results in 42.5%±5 of cells in S-phase versus 29%±2.6 in controls. However, continuous BLIMP1 overexpression appears to slow down the cell cycle.
These findings suggest that BLIMP1 may inhibit proteins that increase DSB and cell death. Our aim is to explore how BLIMP1 expression affects DSB, cell survival, and cell cycle maintenance in WM.
